It is probably doing a disservice to ourselves as Americans to oversimplify issues that cannot, by their very nature, be simple. I have shared examples of passing in America that demonstrate that this behavior is neither new nor unusual. Yes, the image of Rachel Dolezal has meaning. She is consciously constructing blackness with, I believe, integrity and good intentions. If images produce an impact, I believe that the center of all this spectacle around a young academic is the two white parents, estranged from their grown daughter, who publicly "outed" her.

I didn’t know what to say to this, not least because it had been said by the head of donor services at England’s National Health Service Blood and Transplant. The interview was for a book I was writing on blood, a topic I knew a little about by then, but the baldness of his statement still shocked me. Surely we’re all the same under the skin?

I knew the history of race and blood was an ugly one. America’s earliest blood bank, founded in 1937 at Cook County Hospital in Chicago, noted race on donor forms and other blood banks followed suit. During World War II, African-American blood was labeled N for Negro (and some centers refused African-American donors outright) and given only to African-American soldiers. Writing to Eleanor Roosevelt, the chairman of the American Red Cross, Norman H. Davis, admitted that segregating blood was “a matter of tradition and sentiment rather than of science,” but didn’t stop doing it until 1950. Louisiana banned the segregation of blood only in 1972.

But the Red Cross was wrong: While no one is suggesting forced segregation of blood bags, it’s now scientifically established that blood can be racially or ethnically specific…